Using Classic Outlook on Windows for personal email, calendar, and contact management
I just ran into the same issue myself. This change doesn't make any sense whatsoever.
I have 2x Microsoft 365 Business Basic for my two domains. One is handling my own e-mail. and the second is handling my wifes e-mail.
The only reason we pay for Microsoft 365 Business Basic is to be able to have Hosted-Exchange to use our own domains for our e-mails. We have been using Microsoft 365 Business Basic / Hosted-Exchange for years because we find the administration and the use of Exchange Active Sync to be superior compared to using Google, Apple and others using IMAP IDLE is not as efficient with notification handling as Exchange Active Sync.
We haven't had any need to pay for any higher level of Microsoft 365 Business because we already have Microsoft 365 Family which provides access to desktop applications such as Microsoft Outlook. We both also have Microsoft 365 Enterprise E5 via our employer which also allows us to use them on private devices to gain access to desktop applications.
This change is just absurd and completely tonedef. Why on earth should we be required to upgrade our Microsoft 365 Business Basic plans when we already have access to desktop applications via other subscriptions already? To make it even stupider, the "legacy" Microsoft Outlook still functions as normal, allowing for adding Microsoft 365 Business Basic e-mail accounts. It's only the "New Outlook" for Windows that won't allow it. Even "New Outlook" for macOS doesn't block this.
Surely this has to be an oversight and mistake with the latest update to "New Outlook" for Windows?